Well, a person in marketing wants people to be able to send an email to a certain person, so has prepared some copy to make it nice and simple. As such, all they have to do is click a 'send email' button and everything is already there, ready to go.

I'm not the best when it comes to Javascript, php etc. so i thought i'd pursue the html route.

I'd look at setting up a HTML form and using that instead. You can set up a textarea element and have the base text loaded into that and let users edit that as much as they like and then click 'send'. The advantages of this is that you know what's being sent, you can record everything that's sent and you don't have to rely on other peoples PC's doing what they are meant to do.

Also, the "body" attribute isn't standard, and is often unsupported. I know it didn't work for me when my boss asked me to do this, but that was back in...2005-ish.

Also, I don't have an email client on this machine, my mom doesn't have one on hers, my brother doesn't have one on his, etc. People use gmail, not outlook. Your mailto links will annoy me and make my mom think she has a virus. Use a real form.